A method of introducing genes into cells is utilized for elucidating gene function and the nature of proteins encoded by genes and for producing recombinant proteins voluminously. Further, the method of introducing genes into cells is also utilized for introducing a gene of objective enzymes or cytokines into the cells of a subject and producing an objective substance in the body by the genes, thereby to provide the treatment for diseases.
The sequencing of human genomic DNA has been nearly completed and the existence of genes with variously unknown functions is anticipated. Hereafter, the functional analysis of novel human genes is the great challenge in research, but a procedure which can excessively express and knockout genes exhaustively and at high throughput is necessary in order to carry out the functional analysis of genes which extend to several ten thousands of kinds.
Technology of introducing genes into cells is roughly classified into a biological method, namely an introduction method utilizing virus vectors derived from adenovirus, retrovirus and lentivirus, and an introduction method utilizing physical means such as a lipofection method (liposome method), an electroporation method (electric perforation method), a microinjection method and a particle gun method.
Among these, the method utilizing virus vectors is high in the efficiency of gene introduction, but there are drawbacks that the preparation of virus vectors is complicated and problem is found in safety. Although the lipofection method is high in safety, there are drawbacks that the efficiency of gene introduction is low and cell toxicity is strong, and the like.
The direct introduction methods such as a micro injection method and a particle gun method have drawbacks that cell damage is great, the optimization of conditions for efficient introduction of genes is troublesome, and specific technique and instruments are also required with respect to the technical operation.
Further, a conventional electroporation method has adopted a method of arranging a medium in which genes and cells are suspended, between electrodes such as parallel plates, applying electric pulses between both electrodes to produce small pores in the cell membrane and introducing foreign genes into the cells before theyare restored (non-patent literatures 1: EMBO Journal, 1982, Vol. 1, pages 841 to 845; and non-patent literature 2: Bioelectrochem. & Bioenerg., 1999, Vol. 48, pages 3 to 16). Although this method is high in the efficiency of introducing genes, there are drawbacks that the cell damage is great, and the timing and the site of introducing genes are hardly selected freely, etc.
Furthermore, there has been recently developed a transfectional array by which cells are cultivated on a glass substrate on which expression plasmids are printed and genes are introduced into the cells by the lipofection method, in order to analyze the function of genes at high throughput (non-patent literature 3: Nature 2001, Vol. 411, pages 107 to 110). Since this method uses the lipofection method for transfection, the above-mentioned drawbacks caused by the lipofection method still exist.
On the other hand, an alternate adsorption method is reported as a method of immobilizing biological molecules such as nucleic acids and proteins on the surface of a substrate in the state where its activity is kept (non-patent literature 4: Biosensors & Bioelectronics, 1994, Vol. 9, pages 677 to 684). This method is a method of alternately adsorbing polymers with different electrostatic charges on a substrate and sequentially laminating polymer thin films by electrostatic interactions (formation of polyelectrolyte complex), but an example applied for a method of introducing genes has not been reported.